Carbendazim‐loaded electrospun poly(vinyl alcohol) fiber mats and release characteristics of carbendazim therefrom

Ultra‐fine poly(vinyl alcohol) (PVA) electrospun fiber mats containing carbendazim were successfully fabricated by electrospinning from the neat PVA solution containing carbendazim in various amounts based on the weight of PVA. The morphological appearance of both the neat and the carbendazim‐loaded electrospun PVA fibers were smooth and the incorporation of carbendazim in the neat PVA solution did not affect the morphology of the resulting fibers. The average diameters of the neat and the carbendazim‐loaded electrospun PVA fibers ranged between 155 and 160 nm. The chemical integrity of the as‐loaded carbendazim in the carbendazim‐loaded electrospun PVA fiber mats was intact as verified by the ¹H‐nuclear magnetic resonance spectroscopy. Thermal properties of the carbendazim‐loaded electrospun PVA fiber mats were analyzed by differential scanning calorimetry and thermogravimetric analysis. The release characteristics of the carbendazim‐loaded electrospun PVA mats were investigated by the total immersion method in distilled water at 30°C. The carbendazim‐loaded electrospun PVA mats exhibited greater amount of carbendazim released than the carbendazim‐loaded as‐cast films. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrospinning of poly(vinylidene fluoride)/dimethylformamide solutions with carbon nanotubes

For conductive carbon nanotube (CN)/polymer composite fibers to be obtained, CNs were incorporated into poly(vinylidene fluoride) (PVDF) in dimethylformamide (DMF) solutions and electrospun to form CN/PVDF fiber mats. The thinnest fiber was 70 nm thick. The percolation threshold for the insulator‐to‐conductor transition was 0.003 wt % CN for CN/PVDF/DMF solutions, 0.015 wt % CN for CN/PVDF spin‐coated films, and 0.04 wt % CN for CN/PVDF electrospun fiber mats. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1572–1577, 2003     

Controlled release of antibiotics from poly‐ε‐caprolactone/polyethylene glycol wound dressing fabricated by direct‐writing melt electrospinning

Wound dressing, which can release anti‐infectives in a controlled way, is taking an important role in the treatment and recovery of the open wound. An adequate release of antibiotics can prevent infections from microorganisms effectively. Among the new candidates of fabricating base materials for wound dressing, electrospinning fiber mats are attracting numerous attentions for their excellent performance in controlled drug delivery. The drug release behavior of electrospinning fiber mats can be tuned by changing the chemical components and the geometric structures of the mats. In this study, fiber mats with different geometric structures, which composed of poly‐ε‐caprolactone (PCL), polyethylene glycol (PEG), and ciprofloxacin (Cip) with different blending ratios, were successfully fabricated by direct‐writing melt electrospinning, and the release behavior of Cip were subsequently investigated in vitro. The results showed that the addition of PEG improved the hydrophilicity of the mats, which in turn affected the manner of drug release. The presence of PEG changed the releasing mechanism from a non‐Fickian diffusion into Fickian diffusion, which indicated that the diffusion of Cip from the composite fiber mats became the main factor of drug release instead of polymer degradation. Besides, with the same composition but different geometric structures, the drug release behavior is of significant difference. Therefore, all the Cip‐loaded composite fiber mats showed antibacterial activities but with different efficiency. In summary, the release of the drug could be controlled by adding PEG and changing the geometric structures according to the different requirement of wound dressings.     

Methylcobalamin‐Loaded PLCL Conduits Facilitate the Peripheral Nerve Regeneration

The feasible fabrication of nerve guidance conduits (NGCs) with good biological performance is important for translation in clinics. In this study, poly(d ,l ‐lactide‐co‐caprolactone) (PLCL) films loaded with various amounts (wt; 5%, 15%, 25%) of methylcobalamin (MeCbl) are prepared, and are further rolled and sutured to obtain MeCbl‐loaded NGCs. The MeCbl can be released in a sustainable manner up to 21 days. The proliferation and elongation of Schwann cells, and the proliferation of Neuro2a cells are enhanced on these MeCbl‐loaded films. The MeCbl‐loaded NGCs are implanted into rats to induce the regeneration of 10 mm amputated sciatic nerve defects, showing the ability to facilitate the recovery of motor and sensory function, and to promote myelination in peripheral nerve regeneration. In particular, the 15% MeCbl‐loaded PLCL conduit exhibits the most satisfactory recovery of sciatic nerves in rats with the largest diameter and thickest myelinated fibers.     

Chitosan/PEO nanofibers electrospun on metallized track-etched membranes: fabrication and characterization

The development of next-generation adsorption, separation, and filtration materials is growing with an increased research focus on polymer composites. In this study, a novel blend of chitosan (CS) and polyethylene oxide (PEO) nanofiber mats was electrospun on titanium (Ti)-coated polyethylene terephthalate (PET) track-etched membranes (TMs) with after-treatment by glutaraldehyde in the vapor phase for enhancing the nanofiber stability by crosslinking. The prepared composite, titanium-coated track-etched nanofiber membrane (TTM-CPnf) was characterized by Fourier transform infra-red (FTIR), water contact angle, and scanning electron microscopy (SEM) analyses. Smooth and uniform CS nanofibers with an average fiber diameter of 156.55 nm were produced from a 70/30 CS/PEO blend solution prepared from 92 wt. % acetic acid and electrospun at 15 cm needle to collector distance with 0.5 mL/h flow rate and an applied voltage of 30 kV on the TTM-CPnf. Short (15 min) and long (72 h)-term solubility tests showed that after 3 h, crosslinked nanofibers were stable in acidic (pH = 3), basic (pH = 13), and neutral (pH = 7) solutions. The crosslinked TTM-CPnf material was biocompatible based on the low mortality of freshwater crustaceans Daphnia magna. The composite membranes comprised of electrospun nanofiber and TMs proved to be biocompatible and may thus be suitable for diverse applications such as dual adsorption–filtration systems in water treatment.     

Stabilization of electrospun poly(vinyl alcohol) nanofibrous mats in aqueous solutions

<正>The stability ofpoly(vinyl alcohol)(PVA) nanofibrous mats in water media was improved by post-electrospinning treatments.Bifunctional glutaraldehyde(GA) in methanol was used as a crosslinking agent to stabilize PVA nanofiber,but fiber twinning was observed frequently,and the highly porous structure of PVA nanofibrous mats was destroyed when the crosslinked fiber was soaked in water.To overcome this shortcoming,chitosan(CS) was introduced into the PVA spinning solution to prepare PVA/CS composite nanofibers.Their treatment in GA/methanol solution could retain the fiber morphology of PVA/CS nanofibers and porous structure of PVA/CS nanofibrous mats even if they were soaked in aqueous solutions for 1 month.Scanning electron microscopy(SEM),X-ray diffraction(XRD),thermal gravimetric analysis(TGA) and differential scanning calorimetry(DSC) were applied to characterize the physicochemical structure and thermal properties of PVA nanofibers.It was found that the water resistance of PVA nanofibrous mats was enhanced because of the improvement of the degree of crosslinking and crystallinity in the electrospun PVA fibers after soaking in GA/methanol solution.     

Effect of humidity and solvent vapor phase on cellulose esters films

In the present study the effect of relative humidity (RH) during spin-coating process on the structural characteristics of cellulose acetate (CA), cellulose acetate phthalate (C-A-P), cellulose acetate butyrate (CAB) and carboxymethyl cellulose acetate butyrate (CMCAB) films was investigated by means of atomic force microscopy (AFM), ellipsometry and contact angle measurements. All polymer solutions were prepared in tetrahydrofuran (THF), which is a good solvent for all cellulose esters, and used for spin-coating at RH of (35 ± 5)%, (55 ± 5)% or (75 ± 5)%. The structural features were correlated with the molecular characteristics of each cellulose ester and with the balance between surface energies of water and THF and interface energy between water and THF. CA, CAB, CMCAB and C-A-P films spin-coated at RH of (55 ± 5)% were exposed to THF vapor during 3, 6, 9, 60 and 720 min. The structural changes on the cellulose esters films due to THF vapor exposition were monitored by means of AFM and ellipsometry. THF vapor enabled the mobility of cellulose esters chains, causing considerable changes in the film morphology. In the case of CA films, which are thermodynamically unstable, dewetting was observed after 6 min exposure to THF vapor. On the other hand, porous structures observed for C-A-P, CAB and CMCAB turned smooth and homogeneous after only 3 min exposure to THF vapor.     

Microfibrillated cellulose/cellulose acetate composites: Effect of surface treatment

Microfibrillated cellulose (MFC), which consists of a web‐like array of cellulose fibrils having a diameter in the range of 10–100 nm, was incorporated into a cellulose acetate (CA) matrix to form a totally biobased structural composite. Untreated and a 3‐aminopropyltriethoxysilane (APS) surface treated MFC was combined with a CA matrix by film casting from an acetone suspension. The effectiveness of the surface treatment was determined by infrared spectroscopy and X‐ray photoelectron spectroscopy. The Young's moduli of APS treated MFC composite films increase with increasing MFC content from 1.9 GPa for the CA to 4.1 GPa at 7.5 wt % of MFC, which is more than doubled. The tensile strength of the composite film increases to a maximum of 63.5 MPa at 2.5 wt % compared to the CA which has a value of 38 MPa. The thermal stability of composites with treated MFC is also better than the untreated MFC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 153–161, 2010     

Preparation and evaluation of poly glycerol sebacate/poly hydroxy butyrate core‐shell electrospun nanofibers with sequentially release of ciprofloxacin and simvastatin in wound dressings

Biodegradable wound dressing of poly glycerol sebacate/poly hydroxy butyrate was fabricated via the coaxial electrospinning process. Simvastatin and ciprofloxacin were loaded in the core and shell of the fibers, respectively. Scanning electron microscopy and transmission electron microscopy images showed a uniform core/shell structure. Introducing drugs into the polymers would cause the dressing samples to become more hydrophilic and degradation to occur faster. Drugs release would face no interventions, in which, approximately 60% of ciprofloxacin was released during the first 24 hours. Simvastatin exhibited a slower and controlled release behavior, with its release peak recorded after 2 days. The drug‐containing samples showed a proper bactericidal activity against both Gram‐positive and Gram‐negative bacteria. It may be concluded that the drug‐laden wound dressing fabricated in this study is capable of releasing the 2 drugs sequentially and that it is the ideal conditions for controlling infections and reducing wound healing duration.     

Preparation and properties of thermoresponsive and conductive composite fibers with core‐sheath structure

In this research, thermoresponsive and conductive fibers with core‐sheath structure were fabricated by coaxial electrospinning. For preparing the spinning sheath solution, poly‐(N‐isopropylacrylamide‐co‐N‐methylolacrylamide) (PNN) copolymer having thermoresponsive and cross‐linkable properties was synthesized by free‐radical polymerization using redox initiators; it was then mixed with the conductive poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) at different weight ratios in water. On the other hand, poly(butyl acrylate‐co‐styrene) (PBS) copolymer synthesized by emulsion polymerization was dissolved in chloroform and used as the spinning core solution. After electrospinning, the fibers were treated at 110 °C for 1 h to cross‐link the PNN portion in the sheath for strengthening the fibers. Well‐defined core‐sheath fibers were observed from SEM pictures; the outside and inside (core) diameters were 568 ± 24 and 290 ± 40 nm, respectively, as determined from TEM pictures. The fiber mats were further doped by DMSO to enhance their conductivity. For the fiber mat with the weight ratio of PEDOT:PSS/PNN at 0.20 in the sheath, its surface conductivity could reach 29.4 S/cm. In addition, the fiber mats exhibited thermoresponsive properties that both swelling ratio and electric resistance decreased with temperature. Furthermore, the fiber mats exhibited improved flexibility as evaluated via bending test. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1299–1307     

Electrospun fiber mats of poly(3‐hydroxybutyrate), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), and their blends

Electrospinning of poly(3‐hydroxybutyrate) (PHB), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and their blends was first carried out in chloroform at 50 °C on a stationary collector. The average diameter of the as‐spun fiber from PHB and PHBV solutions decreased with increasing collection distance and increased with increasing solution concentration and applied electrical potential. In all of the spinning conditions investigated, the average diameter of the as‐spun pure fibers ranged between 1.6 and 8.8 μm. Electrospinning of PHB, PHBV, and their blends was carried out further at a fixed solution concentration of 14% w/v on a homemade rotating cylindrical collector. Well‐aligned, cross‐sectionally round fibers without beads were obtained. The average diameter of the as‐spun pure and blend fibers ranged between 2.3 and 4.0 μm. The as‐spun fiber mats appeared to be more hydrophobic than the corresponding films and much improvement in the tensile strength and the elongation at break was observed for the blend fiber mats over those of the pure fiber ones. Lastly, indirect cytotoxicity evaluation of the as‐spun pure and blend fiber mats with mouse fibroblasts (L929) indicated that these mats posed no threat to the cells. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2923–2933, 2006     

Thermoresponsive conductive polymer composite thin film and fiber mat: Crosslinked PEDOT:PSS and P(NIPAAm‐co‐NMA) composite

The thermoresponsive conductive composite (TCC) thin films and fiber mats, whose electrical property changed with temperature, were fabricated successfully. The thermocrosslinkable and thermoresponsive copolymer, poly(N‐isopropyl acrylamide‐co‐N‐methylolacrylamide) (PNN), was synthesized. The TCC thin film and fiber mat were fabricated by spin coating and electrospinning process of PEDOT:PSS/PNN solutions, respectively. After thermocrosslinking and doping by DMSO, the composite thin films and fiber mats were obtained. Fibrous structures of TCC fiber mats were observed by SEM. The surface resistance and conductivity of composites were measured. The thermoresponsivity and swelling ratio of TCCs were also studied. The thermoresponsive conductive property was analyzed by measuring the surface resistance of TCCs in water bath under various temperatures from 20 to 50 °C. With the increase of temperature, the TCCs shrank to be dense structure and showed lower surface resistance. The TCC fibers mat exhibited greater sensitivity to temperature than thin film owing to its fibrous structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1078–1087     

Antibacterial and wound healing properties of cellulose acetate electrospun nanofibers loaded with bioactive glass nanoparticles; in-vivo study

Bioactive glasses (BGs) have gained great attention owing to their versatile biological properties. Combining BG nanoparticles (BGNPs) with polymeric nanofibers produced nanocomposites of great performance in various biomedical applications especially in regenerative medicine. In this study, a novel nanocomposite nanofibrous system was developed and optimized from cellulose acetate (CA) electrospun nanofibers containing different concentrations of BGNPs. Morphology, IR and elemental analysis of the prepared electrospun nanofibers were determined using SEM, FT-IR and EDX respectively. Electrical conductivity and viscosity were also studied. Antibacterial properties were then investigated using agar well diffusion method. Moreover, biological wound healing capabilities for the prepared nanofiber dressing were assessed using in-vivo diabetic rat model with induced wounds. The fully characterized CA electrospun uniform nanofiber (100–200 nm) with incorporated BGNPs exhibited broad range of antimicrobial activity against gram negative and positive bacteria. The BGNP loaded CA nanofiber accelerated wound closure efficiently by the 10th day. The remaining wound areas for treated rats were 95.7?±?1.8, 36.4?±?3.2, 6.3?±?1.5 and 0.8?±?0.9 on 1st, 5th, 10th and 15th days respectively. Therefore, the newly prepared BGNP CA nanocomposite nanofiber could be used as a promising antibacterial and wound healing dressing for rapid and efficient recovery.

     

Poly(methyl methacrylate)/silica nanocomposite fibers by electrospinning

Uniform poly(methyl methacrylate) (PMMA)/silica nanocomposite fibers containing up to 20 wt % silica were prepared by electrospinning. The electrospun solutions were prepared by mixing a solution of PMMA in dimethyl formamide (DMF) with colloidal silica in methyl ethyl ketone (MEK). The average fiber diameter decreases from 2.49 μm to 1.69 μm when 20 wt % silica is incorporated as a result of considerably increased solution conductivity, although the solution viscosity increases significantly, which should result in opposite effect. Thinner fibers (down to 350 nm) can be obtained by changing DMF/MEK proportion and by the addition of an ammonium salt. Nano‐sized silica particles (10–40 nm) distributes homogeneously in the fibers, as revealed by transmission electron microscopy. Furthermore, the incorporation of silica nanoparticles can change the thermal properties and surface wettability of the fiber mats. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1211–1218, 2009     

Thermally Tunable Surface Wettability of Electrospun Fiber Mats: Polystyrene/Poly(N‐isopropylacrylamide) Blended versus Crosslinked Poly[(N‐isopropylacrylamide)‐co‐(methacrylic acid)]

This work reports on thermally tunable surface wettability of electrospun fiber mats of: polystyrene (PS)/poly(N‐isopropylacrylamide) (PNIPA) blended (bl‐PS/PNIPA) and crosslinked poly[(N‐isopropylacrylamide)‐co‐[methacrylic acid)] (PNIPAMAA) (xl‐NIPAMAA). Both the bl‐PS/PNIPA and xl‐PNIPAMAA fiber mats demonstrate reversibly switchable surface wettability, with the bl‐PS/PNIPA fiber mats approaching superhydrophobic ≥150° and superhydrophilic contact angle (CA) values at extreme temperatures. Weight loss studies carried out at 10 °C indicate that the crosslinked PNIPAMAA fiber mats had better structural integrity than the bl‐PS/PNIPA fiber mats. PNIPA surface chemistry and the Cassie–Baxter model were used to explain the mechanism behind the observed extreme wettability.

     

Facile Fabrication of Porous ZnS and ZnO Films by Coaxial Electrospinning for Highly Efficient Photodegradation of Organic Dyes

Porous ZnS and ZnO nano‐crystal films were fabricated via a three‐step procedure. First, Zn(CH₃COO)₂/Silk Fibroin nanofiber mats were prepared by coaxial electrospinning. Second, Zn(CH₃COO)₂/Silk Fibroin mats were immersed in NaS solution to react with S²⁻ to obtain ZnS/Silk Fibroin nanofiber mats. Finally, ZnO porous films were prepared by calcination of ZnS/Silk Fibroin composite mat at 600°C in air atmosphere. When ZnS/Silk Fibroin mats were calcinated in nitrogen, ZnS/Carbon composite mats were obtained accordingly. The resulting porous films were fully characterized. The ZnO porous films were the aggregation of ZnO nano‐crystal with hexagonal wurtzite structure. The seize of ZnO was estimated in the range of 10–20 nm. Both of the ZnS and ZnO nano‐crystal films exhibited high photocatalytic activities for the photodegradation of Methylene blue and Rhodamine B. It was also found that ZnO porous films are better than ZnS/Carbon nanofiber mats. In addition, photocatalysis of a real wastewater sample from a printing and dyeing company was conducted. The ZnO porous films exhibited excellent performance to treat the real samples. Moreover, the porous ZnO nano‐crystal photocatalyst could easily be recycled without notable loss of catalysis ability.     

Efficient alternative of antimicrobial nanocomposites based on cellulose acetate/Cu-NPs

The current research presents an efficient, cheap, and safe antimicrobial material for widespread use based on copper nanoparticles (Cu-NPs) loaded on cellulose acetate (CA) matrix. A reduction process of CuSO₄·5H₂O has been performed to prepare Cu-NPs. The nanosized copper particles included oxidized Cu (15–20 nm). Two different loads of Cu-NPs were used in this study, 2% and 6% mol.%. The presence of Cu-NPs incorporated with CA films slightly affected the tensile index of the films, where low and high-loaded Cu-NPs enhanced the tensile index by small values ranged from 0.640 to 0.650 and 0.667, respectively. A study on the antibacterial activity of these nanocomposites was carried out for Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. It has been found that CA containing Cu-NPs (2%) exhibited the highest antimicrobial activity against all test microbes including S. aeureus (21 mm), P. aeruginosa (18 mm), C. albicans (19 mm), and Aspergillus niger (15 mm). Results also revealed that CA film with 6% exhibited lower activity than film with 2% Cu-NPs. The morphological properties of CA/Cu-NPs films were characterized by scanning electron microscopy and transmission electron microscope in addition to X-ray diffraction. Low-loaded Cu-NPs showed homogenous distribution through CA matrix while, the high-loaded Cu-NPs were agglomerated through CA matrix. Thermal properties illustrated the enhancement of thermal stability of the film with increasing the loaded Cu-NPs.     

Preparation of Antimicrobial Ultrafine Cellulose Acetate Fibers with Silver Nanoparticles

Summary: A feasible method for the preparation of antimicrobial ultrafine fibers with silver nanoparticles was developed by direct electrospinning of a cellulose acetate (CA) solution with small amounts of silver nitrate followed by photoreduction. Silver nanoparticles in ultrafine CA fibers were stabilized by interactions with carbonyl oxygen atoms in CA. Ultrafine CA fibers with silver nanoparticles showed very strong antimicrobial activity.

TEM image of an ultrafine CA fiber electrospun from 10 wt.‐% CA solution with 0.5 wt.‐% AgNO₃.     

Fabrication and characterization of UV‐crosslinkable thermoresponsive composite fibers with magnetic properties

Crosslinking magnetic thermoresponsive composite (MTC) fiber mats were fabricated by electrospinning process and followed by UV curing. Thermoresponsive poly‐(N‐isopropylacrylamide) (PNIPAAm) and magnetic Fe₃O₄ were firstly synthesized by redox‐initiated polymerization and co‐precipitation, respectively. A crosslinking agent (dipentaerythritol hexylacrylate) and photoinitiator for providing crosslinking ability were then mixed with PNIPAAm and Fe₃O₄ in ethanol as the electrospinning solution. After electrospinning and subsequent UV irradiation, the MTC fiber mats were thus obtained. Thermoresponsivity of the MTC fibers was measured by both DSC and swelling test. MTC fiber mat exhibited better water‐absorption capability and thermoresponsivity than corresponding film. Morphological analysis was observed by SEM and TEM, and the magnetic property was measured by SQUID. The thermoresponsive magnetic behavior of MTC fiber mat in water was observed under various temperatures and magnetic fields. Vitamin B₁₂ used as a model drug was loaded in the MTC fiber mats and the drug‐release behavior was then studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2152–2162     

Aligned electrospun cellulose fibers reinforced epoxy resin composite films with high visible light transmittance

Uniaxially oriented cellulose nanofibers were fabricated by electrospinning on a rotating cylinder collector. The fiber angular standard deviation (a parameter of fiber orientation) of the mats was varied from 65.6 to 26.2^o by adjusting the rotational speed of the collector. Optically transparent epoxy resin composite films reinforced with the electrospun cellulose nanofibrous mats were then prepared by the solution impregnation method. The fiber content in the composite films was in the range of 5–30 wt%. Scanning electron microscopy studies showed that epoxy resin infiltrated and completely filled the pores in the mats. Indistinct epoxy/fiber interfaces, epoxy beads adhering on the fiber surfaces, and torn fiber remnants were found on the fractured composite film surfaces, indicating that the epoxy resin and cellulose fibers formed good interfacial adherence through hydrogen-bonding interaction. In the visible light range, the light transmittance was 88–92% for composite films with fiber loadings of 16–32 wt%. Compared to the composite films reinforced with 20 wt% randomly oriented fibers, the mechanical strength and Young’s modulus of the composite films reinforced with same amount of aligned fibers increased by 71 and 61%, respectively. Dynamical mechanical analysis showed that the storage moduli of the composite films were greatly reinforced in the temperature above the glass transition temperature of the epoxy resin matrix.